The purpose of this proposal is to develop a vaccine against pandemic influenza viruses to reduce the risk of disease resulting from bioterrorist introduction of virulent influenza strains to a susceptible population. Recent outbreaks of avian influenza in humans have demonstrated the need for vaccines for influenza viruses with pandemic potential. The project objective is to develop a new vaccine for noninvasively immunizing humans against a virulent avian influenza virus by intranasal (IN) inoculation with a replication-defective (rd) adenovirus (Ad) vector expressing the hemagglutinin (HA) gene of the avian virulent H5N1 influenza virus. The mucosal surface is inherently designed to prevent invasion by pathogenic organisms through the development of effective immunity. Its potential to generate both a systemic and local immune response makes the mucosal system an attractive site for immunization. Advantages associated with mucosal vaccination are numerous, including ease and low cost of administration, patient acceptance, avoidance of the hepatic first pass metabolism, and the ability to induce mucosal as well as systemic immunity. Furthermore, the immune response generated at one mucosal site can induce an immune response at distal mucosal surfaces. The process of engineering an rdAd-vector expressing an influenza transgene involves the organic synthesis of a cDNA copy of the influenza HA gene, cloning of the gene into the shuttle plasmid and transfection of packaging-cells with the rdAd-Vector and HA shuttle plasmids to rescue the rdAd-vector expressing the influenza HA gene. Replication-defective Ad-vectored influenza HA vaccines are grown in vaccine substrate qualified mammalian cells, thus facilitating a rapid response to produce new influenza vaccines in a time schedule that cannot be met using egg-dependent methods. As new influenza virus strains emerge, Master Seeds of the rdAd-vectored HA transgene can be rapidly constructed, tested and produced in large scale to be released within a six-month period. Previous clinical studies with rdAd-vectors expressing the HA genes of epidemiologically, relevant influenza viruses have demonstrated the vaccines to be genetically stable, immunologically potent, antigenically authentic and safe. Intranasal immunization with rdAd-vectors expressing HA genes of epidemiologically important influenza viruses induces mucosal and systemic immunity to prevent influenza disease. [unreadable] [unreadable]